The present invention relates to an automatic switching device for the power supply input range of a monitor connected with a personal computer, and especially to an automatic range switching device of a low loss rapidly restoring power supply commonly used in voltages of 110V and 220V.
According to the statistics, nowadays at least 250,000,000 monitors of personal computers are used. Assume the average power consumption of each monitor is 50V, the total power consumption will be a very great number. Thus many consumer organizations and energy management institutions have called for reducing the power consumption.
In order to be conveniently manufactured and sold, and to prevent the consumer from making a mistake while using, the specifications of the globally used monitors are called "Auto Range": AC110V.+-.20% and AC220V.+-.20%, or Full Range: AC86V.about.264V. This wide range of power supply design can't meet the purpose of using the least power of the monitors. The following table lists the power circuits of commercial monitors:
TABLE 1 MAX. MAX. Input range horizontal Power of power Brand Size frequency consumption supply OPTIQUEST 17" 69 KHz 80 W AUTO V775 TATUNG 17" 94 KHz 105 W AUTO 17N APPLE 15" 48 KHz 70 W FULL M2943 TATUNG 15" 64 KHz 75 W FULL 15VHR
NOTE 1: The circuit control of automatic range is shown in FIG. 1a. If the input voltage of the power supply is 110V, the Triac I.sub.801 turns on to make the circuit become a voltage doubler. If the power source is 220V the Triac I.sub.180 cut off, the circuit become bridge rectifier.
NOTE 2: The full range circuit control is shown in FIG. 1b. No matter whether the input voltage of power source is 100V or 220V, the circuit functions as the bridge rectifier.
In the auto range controlling, when the input power source is 110V(i.e. 110V.+-.20% ), the rectifying circuit does the function of a voltage doubler, so that the output voltage is the same as that from a 220V power source (i.e. 220V.+-.20% ). Now referring to FIG. 1a, the voltage value of Vc is in the range of 2.times.220V.times.(1.+-.20% )=249V.about.373V. This value is different from that in the full range, in which VC=124V.about.373V. When the input voltage of the power source is 100V, the current consumption in the full range is approximately twice that in the auto range. For, example, in the OPTIQUEST V775 with power consumption of 80 W, the former has a current of 1.06 A, while the latter has a current of 0.53 A. However, when the input voltage of the power source is 220V, both have a power consumption of 0.53 A. As shown in Table 2, assuming that the power consumption is 80 W for the two circuits, the specifications of the related components are listed as follows
TABLE 2 Specification control Auto range Full range circuits (A) (B) Description Power Q805 = Q805 = When input is 110 V, the transistor 4A/500 V 8A/500 V current of B circuit is twice of that of A Circuit. Filtering C809 = C808 = Since Cv = it , when 110 V capacitor 150.mu./200 V 300.mu./400 V power input, the voltage of B C810 = circuit will be halved, while 150.mu./200 V when i is doubled, then the voltage of C is four times of that of A circuit. output end D811 = D811 = The number of windings in rectifier 100 V 1A 200 V 1A the primary terminals of A/B D812 = D812 = circuits are 116 and 231, 200 V 1A 400 V 1A respectively, while in the secondary terminal, A/B circuits has the same winding numbers. That is in the primary terminal, the ratio of winding number A/B is 0.5. When input is 220 V, the reverse voltage of B circuit is twice of that of A circuit. Voltage 1802 = unnecessary When input is 110 V, the A multiplier 10A/500 V circuit need a voltage and switch (STR81145A) multiplier and switch.
In table II, for the sizes of the parts used in the A and B circuits, the larger the size, the more expensive the cost. Thus the cost is the primary concern in selecting a circuit. After analyzing, it is known that the power consumption is smaller than 80 W, the circuit has an economic cost by using the full range control, and vice versa.
But from the viewpoint of energy saving, no matter whether the control circuit is operated in full range or in auto range, the prior circuit structures are not preferable. Following are the explanations:
For the circuit operating in auto range: referring to FIG. 2a, a voltage multiplying and switch device(I.sub.801), such as integrated circuit STR80145A. is used. Since a triple directional silicon control rectifier (Triac) is built therein and a voltage decreasing resistor is connected, some loss will occur, as shown in FIG. 2b.
For the circuit operating in full range: in the highest efficiency, the voltage is in a middle range between 88V.about.264V; this range is between the range of the 132V.about.176V. When the voltage of power supply is closer to an upper limit or a lower limit, the power consumption is larger and the efficiency will become worse.
Table 3 may prove the above description. For example, for a monitor operated in auto range (17 inches monitor), when the power supply is AC110V, the average power consumption is larger than that in of a power supply of AC220V with a value of ##EQU1##
Also, for a for monitor operated in full range (15 inches monitor) with a lower limit of 88V and an upper limit of 264V, then the average power consumption is larger than that operated in the range of AC132V.about.AC176V with a value of ##EQU2##
TABLE 3 Pattern cross hatch; Timing: F.sub.H = 31.5 KHz; F.sub.V = 70 Hz Input power supply voltage Specification AC110 V AC220 V Max. Lower Upper Lower Upper Size horizontal limit limit limit limit Brand (inch) freq. Rectifier 88 V 132 V 176 V 264 V OPTIQUEST 17" 69 KHz Auto range 1.097 A 0.769 A 0.554 A 0.369 A V775 66.6 W 67.1 W 64.5 W 66.3 W TATUNG 17" 94 KHz Auto range 1.503 A 1.028 A 0.746 A 0.499 A 17N 97.6 W 94.7 W 91.4 W 92.2 W APPLE 15" 48 KHz Full range 1.025 A 0.699 A 0.517 A 0.353 A M2943 61.5 W 59.8 W 60.0 W 63.0 W TATUNG 15" 64 KHz Full range 0.956 A 0.657 A 0.488 A 0.335 A 15VHR 59.2 W 57.6 W 57.7 W 59.7 W